What is the recommended workup for an enlarged thyroid?

Workup for Enlarged Thyroid

The initial workup for an enlarged thyroid should begin with serum TSH measurement, followed by thyroid ultrasound to assess gland morphology, nodule characteristics, and cervical lymph nodes. 1

Initial Laboratory Testing

• Measure serum TSH first as the single most important screening test to determine thyroid functional status 2, 3, 4

  • If TSH is abnormal (elevated or suppressed), add free T4 (fT4) to characterize the degree of dysfunction 3
  • In hyperthyroid patients (low TSH), also measure total T3 or free T3 to detect T3 toxicosis 2
  • TSH alone has 98% sensitivity and 92% specificity for detecting thyroid dysfunction 1

• Consider thyroid autoantibodies (anti-TPO) if TSH is elevated, as this identifies Hashimoto's thyroiditis as the cause of hypothyroidism 4

• Measure serum calcitonin if medullary thyroid carcinoma is suspected, though routine screening remains controversial in the United States due to lack of available pentagastrin for confirmatory testing 1

Imaging Studies

• Thyroid ultrasound is essential for all patients with thyroid enlargement 1

  • Evaluates thyroid size, echotexture, and presence of nodules
  • Identifies suspicious features requiring biopsy: microcalcifications, irregular borders, central hypervascularity, taller-than-wide shape 1
  • Assesses cervical lymph nodes for metastatic disease 1

• Fine needle aspiration (FNA) biopsy should be performed on:

  • Any nodule with suspicious ultrasound features regardless of size 1
  • Clinically suspicious lymph nodes 1
  • The decision to biopsy should be based on nodule size thresholds and ultrasound risk stratification per established guidelines 1

Additional Testing Based on Functional Status

For hyperthyroid patients (suppressed TSH):

• Radioactive iodine uptake and scan can differentiate Graves' disease (diffuse increased uptake) from toxic nodular goiter (focal uptake) or thyroiditis (low uptake) 1
• Doppler ultrasound showing increased thyroid blood flow suggests active hyperthyroidism rather than destructive thyroiditis 1

For hypothyroid patients (elevated TSH):

• No imaging is indicated beyond ultrasound if already performed 1
• Imaging does not help differentiate causes of hypothyroidism 1

Risk Stratification for Malignancy

Clinical features that increase malignancy risk include: 1

• Age <15 years or male gender
• Very firm nodule fixed to adjacent structures
• Rapid growth
• Enlarged regional lymph nodes
• Vocal cord paralysis or symptoms of neck structure invasion
• Family history of thyroid cancer or associated syndromes (MEN 2, familial adenomatous polyposis, Cowden syndrome)
• History of head and neck irradiation

Common Pitfalls to Avoid

• Do not order comprehensive thyroid panels routinely - TSH alone is sufficient for initial screening in most cases 2, 3

  • Studies show 80% of patients have normal TSH when full panels are ordered unnecessarily 2

• Do not rely solely on T3 measurements - T3 toxicosis occurs in only 8% of hyperthyroid cases, and low T3 syndrome in hospitalized patients is uncommon (1.6%) 2

• Do not skip ultrasound even if thyroid function tests are normal - structural abnormalities requiring intervention may exist independent of function 1

• Do not assume all low TSH values indicate hyperthyroidism - elderly patients frequently have suppressed TSH without true thyroid disease 3

Surgical Evaluation

For goiters causing compressive symptoms: 5

• Document symptoms: dyspnea, orthopnea, dysphagia (more common with substernal extension)
• Preoperative assessment should include evaluation of airway patency and vocal cord function
• Consider CT or MRI for substernal goiters to assess tracheal deviation and compression